The present invention relates generally to the design and construction of a lightweight high temperature retainer for a rotor disk assembly. More particularly, the present invention has one form wherein a low-density high temperature segmented ring retainer resists the axial displacement of a gas turbine engine's compressor and turbine blades. Although the present invention was developed for a gas turbine engine, certain applications may be outside this field.
The gas turbine engine is representative of the type of machinery in which the present invention may be advantageously used. A conventional gas turbine engine integrates a compressor and a turbine that have components that rotate at extremely high speeds. The compressor is operable to compress air to the proper pressure required for supporting the combustion of fuel in a combustion chamber. A high temperature gas exiting the combustion chamber provides the working fluid for the turbine, and may also be used to drive a power turbine. The power turbine drives a propeller, fan, or other device. Further, the high temperature gas may be used directly as thrust for providing motive power, such as in a turbine jet engine.
A gas turbine engine rotor assembly conventionally comprises a plurality of circumferentially spaced airfoils, which extend radially outward from a rotor disk. During engine operation, the rotor assembly is rotated at a high speed, thereby creating a centrifugal force acting on the components. Axial forces are imparted to the airfoils as the fluid passes through the rotor assembly.
The rotor assemblies often include a dovetail or firtree attachment mechanism for coupling the components together and resisting the centrifugal force acting on the components. Many prior designs have included axial retaining mechanisms such as rivets, bolts, tangs, pins and split rings to counteract axial loads on the airfoil. The utilization of mechanisms such as rivets, bolts and pins can introduce stress concentration cites which lead to fatigue life limitations. The tang type axial retaining mechanisms generally require additional adjacent structure to provide the necessary restraint in the fore and aft direction.
Split ring retainer systems generally include a retaining hook formed around the periphery of the rotor disk. The split ring retainer is deflected to a size appropriate for insertion into the retaining hook, and upon release is positioned within the retaining hook to resist axial displacement of the airfoils. The split ring retainers have generally been formed from steel or nickel materials so as to have the required strength for load resistance and ductility for deflection.
The high-speed rotation of the rotor assembly causes a centrifugal load associated with the tang type and split ring type retainer that must be carried by the airfoil attachment mechanism. Further, increased compressor pressure ratios require the utilization of retainers having improved temperature capabilities. Thus, it is desirable to incorporate low-density high temperature materials into the airfoil retaining systems. Low-density high temperature materials with the necessary strength for gas turbine engine airfoil retainers generally do not possess the requisite ductility for use in split ring retainers.
Heretofore, there has been a need for a lightweight, high-temperature retaining mechanism for a gas turbine engine rotor assembly. A means for satisfying this need has theretofore escaped those skilled in the art. The present invention satisfies this need in a novel and unobvious way.